Apparatus for temporarily reducing the volume of a synthetic material container

ABSTRACT

After filling and before closing of a container of synthetic material, the volume of the container is reduced, by an amount corresponding to the reduction in volume on cooling of the container to reduce or prevent undue pressure in the closed container. Pressure can be applied pneumatically or mechanically to produce the reduction in volume.

United States Patent 1 1111 3,717,430

Hansen 1 1 Feb. 20, 1973 54] APPARATUS FOR TEMPoRARILY [56] References 1211611 REDUCING THE VOLUME OF A UNITED STATES PATENTS 3,583,036 6/197! Brown ..l8/5 BZ SYNTHETIC MATERIAL CONTAINER [76] inventor: Gerhard Hansen, D 7013 Oeffingen,

3,277,534 10/1966 McDonald et al. .....1s/s BB ux Krels walblmgen, 3,032,809 5/1962 Willard ..18/5 1313 UX Germany 3,325,860 6/1967 Hansen ..l8/5 BF [22] Filed; My 1970 3,331,902 7/1967 Stark ....1s/s BF x 2,425,610 8/1947 Finley ....249/1ss x PP 54,796 3,241,187 3/1966 Nouel ..18/l6 R Primary Examiner-Rpbert L. Spicer, Jr.

[ Foreign Application Priurity Dam Attorney-Watson, Cole, Grindle and Watson July l 8, l969 Gerriiariy 30 648.4 57 ABSTRACT [52] U.S. Cl. ..425/392, 425/156, 425/326, Aftcr filling and f r l g of a c n iner of 425/388, 425/395, 425/406, 425/441, synthetic material, the volume of the container is 425/450 reduced, by an amount corresponding to the reduction [51] Int. Cl. ..B29d 23/00 in volume on cooling of the container to reduce or Field of Search 149/155, 1 prevent undue pressure in the closed container. Pres- 18/5 5 32? 425/326 3871 3271 393, sure can be applied pneumatically or mechanically to 3957 156 produce the reduction in volume.

5 Claims, 4 Drawing Figures IF .T 1 50412:: c: H nan M Vi 1 1 .1 L 1 I 2 l 1 l I l l 5L. J 17a 1 I II l 1 l II I Ill: d 1 i 4 720 M :m 5 i l I 1 1 l 2// V 1 A: sou 7c; a; y L 5 22222 2,?

APPARATUS FOR TEMPORARILY REDUCING THE VOLUME OF A SYNTHETIC MATERIAL CONTAINER The present invention relates to methods of and apparatus for temporarily reducing the volume of a synthetic material container located in a closed hollow mould, in particular shortly before closure of the container.

A variety of synthetic materials shrink during cooling. When a cooling, closed, container shrinks in this way, its volume becomes smaller and there is thus a risk that an undesirably high pressure will develop inside the container, leading to bulging and the like. In particular in the case of round-section containers, there is a tendency for the bottom or base to bulge outwards, impairing its stacking or standing properties. In the case of containers having oval or slightly convex or for that matter flat surfaces, the surfaces which will yield most readily tend to distort so that the appearance of the container must be impaired.

According to one aspect of the invention there is provided a method of temporarily reducing the volume of a synthetic material container located in a closed hollow mould in which a pressure sufficient to produce a shrinkage corresponding to the shrinkage of the container when closed, on cooling, and lasting at least until the closing thereof, is exerted on at least part of the belly of the container.

According to another aspect of the invention apparatus for temporarily reducing the volume of a synthetic material container in a closed hollow mould comprises at least one wall section of the hollow mould located in the neighborhood of the belly of the container, a drive motor for displacing the wall section towards the container and arranged to maintain the section for a controlled time in the displaced position in dependence upon the shrinkage of the container, which position is determined by a stop element.

In one embodiment, by means of the pressure, the volume of the open container is reduced until it is closed. The closed, now pressureless container, then initially has a larger volume so that excess pressure can only develop inside it as a consequence of shrinkage if the container shrinks to a greater extent than corresponds with the preceding increase in volume. The shrinkage volume and enlargement volume can be adapted to one another so that the container can be kept virtually free of internal pressure even when very fully filled.

The pressure to be exerted upon the container prior to its closure, can be produced in a variety of ways. For example, considering a container which is blowmoulded using at least an externally applied vacuum, the inflated belly of the container can be maintained at superatmospheric pressure. It is equally possible, however, to apply the desired pressure mechanically.

By means of a wall section, a mechanical pressure may be exerted upon the container. This measure has the advantage that the displacement travel of the wall section is limited and can be accurately adjusted so that the desired effect is achieved within the limits determined by the shrinkage process and within narrow tolerances. The wall section is adapted to the external form of the container so that the container shape is not undesirably affected by same.

The invention may be performed in various ways and one specific embodiment, with modifications, 'will now be described by way of example with reference to the accompanying diagrammatic drawings of a device for the temporary reduction of the volume of a container, and in which:-

FIG. 1 is an elevational cross-sectional view of a production mold constructed in accordance with the present invention taken substantially along line I-I of FIG. 2, but not showing the extrusion press or the supply and filler device which are illustrated in FIG. 2;

FIG. 2 is a cross-sectional view taken substantially along line 11-11 of FIG. 1, and further showing schematically the conventional extrusion press and supply and filler device with which the present invention is used as well as a length of tubing of synthetic material in its original, as extruded form;

FIG. 3 is a side elevation of part of the production mould; and

FIG. 4 is a cross-section on the line IV-IV of FIG. 3.

Referring to the drawings, a slide 2 can be displaced on a table 1 by means of a control cylinder 3, from a position beneath an extrusion press 4, to a position beneath a supply and filler device 5, the press 4 and supply and filler device 5 being conventional and no further description need to given.

The slide 2 carries two bottom mould halves l2 and 12a of a hollow mould which are displaceable transversely of the direction of displacement of the control cylinder 3. The bottom mould halves carry a suction head 14, respectively between which and the associated bottom mould half a respective top mould half 16 or 16a can be displaced in the same direction as the bottom mould halves 12, 12a. The bottom mould halves 12, 12a, the suction heads 14, 14a and the top mould halves 16, 16a are connected through vacuum sources controllable as desired and at will. The bottom mould halves 12, 12a and the suction heads 14, 140 can be directly connected with one another.

The bottom mould half 12 can be displaced independently by a control cylinder 17 and the top mould half 16 similarly be displaced independently by a control cylinder 18.

The parts of the production mould shown at the right hand side in FIG. 1, are given the same references as the parts shown at the left, the references of the righthand parts also carrying the letter a.

A wall section 26, provided for the formation of the belly of the container and located in the bottom mould half 12, is mounted in said mould half in such a manner as to be displaceable in the direction of the arrow A in FIG. 4, and to this end has guide surfaces corresponding to the outer parts of the bottom mould half. The wall section 26 can, for purposes of displacement within the closed production mould 12, 12a, be arranged to form only a limited part of the mould wall which is intended to mould the container.

The wall section 26 has outward-projecting arms 27 and 28 with which control cylinders 29, 30 which act as drive motors and are fitted to the bottom mould half 12 respectively engage. At the side remote from the control cylinders 29, 30 are respectively fitted mounting arms 31, 32, each of these arms carrying a screw 33 to act as an adjustable stop element vis-a-vis the arm 27 or 28 to limit or determine the displaced position of wall section 26. The screws 33 of the two co-operating bottom mould halves l2 and 12a may possibly be arranged at different heights or positions in order not to interfere with'the closing of the production mould.

The remaining parts of the production mould are conventional and need not be described in detail.

In the selected example, at the commencement of the operating cycle the open production mould is located below the die orifice of the extrusion press 4, which produces a section of tube 6 of synthetic plastics material. As soon as the extruded tube 6 is sufficiently along, the two bottom mould halves 12;, 12a traverse together. In order to inflate the tube section 6 to form a container, a vacuum is applied to the external surface of the tube 6 through the bottom mould halves 12, 12a. The top mould halves 16, 16a, although picked up and carried along with the bottom mould halves 12, 12a, are not closed. The tube section 6 is held at its top end by the suction heads 14, 14a which have been traversed together, before it is separated from the extrusion press by suitable means.

The production mould then passes beneath the tiller element which is lowerable such that its mouth rests on the bottom mould halves 12, 12a through the intermediary of the tube of synthetic material. By means of the filler element, compressed air is blown in, possibly until the container belly has been fully inflated, and the arrangement may be such that the air can only escape from the container by overcoming a certain back pressure. Thereafter, the material with which the container is to be filled is supplied into thebelly of the container, displacing the air (possibly compressed air), as it does so. After the filling of the container, the tiller element 5 is lifted away. Before the closing of the top mould halves 16, 16a to form the top of the container, and thus close the container, the control cylinders 29, 30 are operated and the wall sections 26, 260 are displaced so that the volume of the belly of the container is reduced. The displacement of only one of the wall sections may possibly suffice. Only then are the top mould halves 16, 16a closed in order to form the top of the container,-and the exterior of the latter is exposed to a vacuum. The filled and closed container is ejected by opening the production mould. Any container which happens to stick in the mould can be removed by moving the wall section 26 backwards and forwards. The movable parts of the production mould, after the ejection of the finished container, revert to their initial positions. As soon as the production mould arrives beneath the extrusion press 4, a new cycle can be started.

The wall section 26 is displaced by an amount corresponding to the reduction in volume of the closed container on cooling, and possibly to the volumetric change in the filler material on assuming the environmental temperature. In this way a pressure is exerted on the container sufficient to produce a reduction in volume of the container corresponding to the reduction in volume of the containeron cooling when closed, and possibly in addition to the volumetric change of the filler material. The pressure is exerted on at least part of the belly of the container for a controlled time and lasts at least until the container is closed. The wall section or sections 26 and 26A are maintained in their displaced position(s) for a redetermined controlled time in dependence on the s rmkage of the container, the

position(s) being determined by the stop elements. In this fashion, the development of a pressure inside the container, with resultant distortion of the latter, is counteracted.

In the bottom mould half 12, or 120, which has a vacuum chamber with bores leading to the wall which forms the container, the container can, instead of or in addition to the mechanical deformation, be briefly subjected, prior to the closure of the top mould halves 16, 16a, to a slight superatmospheric pressure of for example mm of water, which is chosen so as to produce a shrinkage corresponding with the shrinkage of the container material and the volumetric change of the substance with which the container is filled.

I claim:- I. Mold apparatus for use in connection with a machine for molding, filling and sealing containers, said apparatus comprising:

movable lower mold sections mounted for radial movement between open and closed positions for enclosing the lower part of a length of tubing of synthetic material therebetween when closed;

means for moving said lower sections between said positions;

movable upper mold sections mounted for radial movement relative to said lower sections between open and closed positions for enclosing the upper part of said length of tubing therebetween when closed;

means for moving said upper sections between said positions; and

separate force applying means carried by at least one of said lower mold sections, said force applying means being operable when the mold sections are in their closed position for applying an inwardly directed force on an area of said lower part of said length of tubing whereby to reduce the inner volume of the latter while the same is enclosed by the closed mold sections.

2. Apparatus as set forth in claim 1 wherein said means for applying the inwardly directed force comprises a relatively inwardly movable wall portion carried by one of the lower mold sections and means for moving said wall portion toward the length of tubing when the lower sections are in their closed positions.

3. Apparatus as set forth in claim 2 wherein is included stop means operably connected to said portion of the wall to limit the movement of the latter in a direction toward said length of tubing.

4. Apparatus as set forth in claim 3 wherein said stop means is adjustabie.

5. Apparatus as set forth in claim I wherein is included means for controlling the amount of time said force is applied to said length of tubing. 

1. Mold apparatus for use in connection with a machine for molding, filling and sealing containers, said apparatus comprising: movable lower mold sections mounted for radial movement between open and closed positions for enclosing the lower part of a length of tubing of synthetic material therebetween when closed; means for moving said lower sections between said positions; movable upper mold sections mounted for radial movement relative to said lower sections between open and closed positions for enclosing the upper part of said length of tubing therebetween when closed; means for moving said upper sections between said positions; and separate force applying means carried by at least one of said lower mold sections, said force applying means being operable when the mold sections are in their closed position for applying an inwardly directed force on an area of said lower part of said length of tubing whereby to reduce the inner volume of the latter while the same is enclosed by the closed mold sections.
 1. Mold apparatus for use in connection with a machine for molding, filling and sealing containers, said apparatus comprising: movable lower mold sections mounted for radial movement between open and closed positions for enclosing the lower part of a length of tubing of synthetic material therebetween when closed; means for moving said lower sections between said positions; movable upper mold sections mounted for radial movement relative to said lower sections between open and closed positions for enclosing the upper part of said length of tubing therebetween when closed; means for moving said upper sections between said positions; and separate force applying means carried by at least one of said lower mold sections, said force applying means being operable when the mold sections are in their closed position for applying an inwardly directed force on an area of said lower part of said length of tubing whereby to reduce the inner volume of the latter while the same is enclosed by the closed mold sections.
 2. Apparatus as set forth in claim 1 wherein said means for applying the inwardly directed force comprises a relatively inwardly movable wall portion carried by one of the lower mold sections and means for moving said wall portion toward the length of tubing when the lower sections are in their closed positions.
 3. Apparatus as set forth in claim 2 wherein is included stop means operably connected to said portion of the wall to limit the movement of the latter in a direction toward said length of tubing.
 4. Apparatus as set forth in claim 3 wherein said stop means is adjustable. 